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David Letterman may have lost his voice on Wednesday night but he didn't lose his ability to disguise serious questions with a drape of humor.

The funnyman of late night television hosted Tesla Motors CEO Elon Musk on his show and while Letterman mostly let him sing the praises of his car company for 10 minutes, the funnyman pushed Musk on several issues.

Letterman, who had lost his voice earlier in the day, pushed Musk to explain why his car costs so much and if it really is better for the enviroment than a hybrid.

"Actually even if 100% of the electricity comes from coal, the Tesla Roadster, which is a sports car, produces less Co2 than a Prius," Musk said.

Letterman pushed him more about when a practical Tesla car would be made that the non-Hollywood crowd could get their hands on one.

"When you have new technology it takes time to make it lower cost and mass market," Musk said. "You know you think of the early days of cell phones or laptops, it takes time to cut costs."

And Musk told Letterman that the few who can afford the $100,000 Tesla Roadster now should feel good about their investment because they are helping the company develop cars for the rest of us little people.

And when will this magical lower cost car be available? A "couple of years," according to Musk.